The present invention relates to a detector which is adapted to detect whether a gas or a liquid is present in a fluid delivery conduit. The detector of the present invention is particularly suited for use as a low cost air-in-line detector in intravenous flow control equipment for delivering intravenous fluid to patients.
In administering intravenous fluid to patients, it is important to monitor the fluid being administered for the presence of air because if air is infused into a patient, an embolism can occur. Air can be introduced into a system through a leak in a tubing connector, through a crack in the equipment, or when the container from which the fluid is delivered is emptied. In some cases, particularly with flexible walled IV containers, the container is not completely filled at the factory, leaving an air space. This air may be infused into the patient if the fluid is delivered with a volumetric pump.
However, optical detectors can often produce false air-in-line signals when the tube or conduit is actually filled with liquid. Some IV fluids scatter and do not focus light, particularly IV fluids which contain particulates. Some IV fluids may be semi-opaque. The result is that the detector cannot distinguish between a liquid filled and an air filled conduit.
Furthermore, optical detectors of the type described above require the use of clear plastics in the liquid conduit. However, many useful medical grade plastics are not clear, so an optical detector cannot be used with them.